#include<stdio.h>
/* 全局变量声明*/

int a = 20;

int main()
{
    /* 在主函数的局部变量声明*/
    int a = 10;
    int b = 20;
    int c = 0;
    int sum(int, int);

    printf("value of a in main() = %d\n", a);
    c = sum(a,b);
    printf("value of c in amin() = %d\n", c);

    return 0;
}

/* 添加两个整数的函数*/
int sum(int a, int b)
{
    printf("value of a in sum() = %d\n", a);
    printf("value of b in sum() = %d\n", b);

    return a + b;
}